Explosive actuated tool and method for driving a stud element



2 Sheets-Sheet 1 J. F. HELDERMAN ET AL Feb. 10, 1970 ExPLosIvE ACTUATED TOOL AND METHOD EDR DRIVING A STUD ELEMENT Filed May 2, 1968 Fb Agr'nNEw/S Fehvl, 1970 J. F. HELDERMAN ET AL 39494,(3

EXPLOSIVE ACTUATED TOOL AND METHOD FOR DRIVING A STUD ELEMENT Filed May 2, 1968 2 Sheets-Sheet 2 INVEN'roRs JAMES F. NELDERMAN E. wlLLnAM E.. BROOKS BY 3,494,018 EXPLOSIVE ACTUATED TOOL AND METHOD FOR DRIVING A STUD ELEMENT James F. Helderman and William E. Brooks, York, Pa.,

assgnors to U.S. Expansion Bolt Company, York, Pa.,

a corporation of Pennsylvania Filed May 2, 1968, Ser. No. 726,088 Int. Cl. B231: 1.7/; B25c 1/02; F41f 1/00 U.S. Cl. 29--432 14 Claims ABSTRACT 0F THE DISCLOSURE An explosive actuated tool for driving stud elements by percussion ignition of a charge by inward movement of a stud element against the charge upon striking the tool with a hammer while a projecting end of the stud element is in engagement with a work surface. Firing of the tool by inadvertently striking the tool or the projecting stud element is prevented by an initial positioning of the stud element at a spacing from the charge, this position being obtained by a tapered bore surface at which a guide washer frictionally carried by the stud element is seated, 4with the frictional resistance of the guide washer preventing a tiring impact of the charge by the stud element upon an inadvertent initial inward movement of the stud element. To purposely actuate the tool, two hammer strikes against the tool are required with the rst strike moving the stud element inwardly without igniting the charge to a position at which the second strike will cause ignition impact of the charge. Further, a firing pin adapter member is mounted on the inner end of the stud element to occlude the spacing between the stud element inner end and to present a protuberance that adapts the stud element for ignition impact with the charge.

Background of the invention The present invention relates to an improvement in an explosive-actuated tool of the type described and claimed in U.S. Patent No. 3,172,123, issued Mar. 9, 1965, by which a fastener stud element is driven into a work piece by the expanding gases obtained from the ignition of an explosive charge that is ignited by impact of the stud element aganist the charge. This tool includes a barrel member having a bore in which the fastener stud element is received, and a chamber communicating with the bore at the inward end thereof, this chamber being shaped to receive and position a percussion ignitable explosive charge for ignition by the impact received as a result of inward movement of the stud element in the bore. The impact producing inward movement of the stud element is obtained by forming the bore with a length that is slightly less than the length of the stud element whereby the tip end thereof extends outwardly beyond the end of the barrel member, and by ring the tool with this extending tip end of the stud element held in contact with the work surface into which it is to be driven as, for example, by hitting the rear end of the barrel member with a hammer so as to drive the stud element into the bore to ignite the charge by the impact of the stud element against the charge.

Although the design of the tool of the aforementioned patent is such it will not fire unless the extending tip end ice of the tool or stud element is struck with a firm and strong blow, careless handling of the tool could result in the extending tip end of the stud element being inadvertently struck against a rigid object with suflicient force to ignite the explosive charge prematurely, as, for example, if the tool is accidentally dropped so that the extending tip end of the stud element strikes a hard surface such as a concrete oor, thereby tiring the stud element from the tool and possibly causing physical damage or personal injury.

In addition, some diiculty has been encountered in satisfactorily adapting some forms of stud elements for use in these tools where the head portions of the stud elements are smaller in diameter than the barrel member bore and thereby permit the explosive gases to escape around the head portion rather than drive the stud element, and where the head portion is not formed with a protuberance which will provide the necessary impact to ignite the explosive charge.

By the present invention, the possibility of a premature ignition of the tool is substantially eliminated, and a firing adapter member is provided which removes the aforementioned diiculties encountered in adapting some forms .of stud elements for use in the tool.

Summary of the invention According to the present invention, the explosive actuated tool of the aforementioned type is provided with means for restraining the stud element in an initial position in the barrel member bore so that the tip end of the stud element extends outwardly beyond the barrel member as was previously the case, but with the head end of the stud element spaced from the percussion ignitable explosive charge, this means also providing frictional resistance to movement of the stud element inwardly in the bore so that when the extending tip end of the stud element is first contacted it will move inwardly in the bore from its initial position to a pre-firing position without igniting the charge, the tip end of the stud element having a reduced outward extent at this pre-firing position and the head end of the stud element being disposed substantially adjacent the charge at this position whereby the stud element will ignite the charge when the tip end of the stud element is forcefully contacted to cause further inward movement .of the stud element in the bore.

In the disclosed embodiment of the present invention, the barrel member bore includes an outwardly flared frusto-conical surface portion formed adjacent the outer end thereof and coaxially therewith, and the stud element includes a guide washer intimately associated therewith so as to offer frictional resistance to movement of the stud element relative to the guide washer whereby when the stud element is placed in the bore, the guide washer will be engaged by the frusto-conical surface portion of the bore for initially holding the stud element at its aforementioned initial position. Then, when the extending tip end of the stud element is forcefully contacted so as to cause inward movement of the stud element (i.e., if the tool is inadvertently dropped or struck against a rigid object), the frusto-conical surface portion will hold the guide washer in place and the stud element will encounter frictional resistance to initial inward movement thereof as a result of its intimate association with the guide washer, and this frictional resistance opposes the tendency of the stud element to be moved inwardly against the charge with sufficient impact to ignite the charge. Upon the extending tip end of the stud element being forcefully contacted a second time, the stud element will move inwardly in the bore with sufficient force to ignite the charge.

Thus, it will be seen that the tool of the present invention has a significant built-in safety feature in that even if the extending tip end of the stud element carried in the tool is inadverently struck against a rigid object, the stud element will simply move inwardly to its pre-firing position without prematurely igniting the charge.

On the other hand, the user of the tool can purposely ignite the charge readily by positioning the tool with the extending tip end of the stud element held against a work surface, and then striking the barrel member twice with a hammer or similar implement. In this regard, it should also be pointed out that this double strike feature of the present invention minimizes the possibility of stud element ricochet because the initial strike against the barrel member usually results in the point of the stud element making a slight indentation in the work surface, and this indentation serves to help guide the stud element directly into the work surface when the charge is ignited by the second strike against the barrel member.

The present invention also provides a firing adapter member which makes it possible to use with the tool of the present invention a conventional type of stud element that ordinarily is unsuited for such use because it has a head end portion that is not formed with the necessary protuberance to fire the explosive charge and that has an external diameter which is smaller than the interior diameter of the barrel member bore.

In accordance with the present invention, the firing adapter member includes a body portion formed to extend around the head end of the stud element so as to align the stud member properly therein and to occlude the spacing between the head end and bore, and an end portion formed to present a protuberance at the end face of the stud element head end for impact ignition with the explosive charge.

In one disclosed embodiment of this ring adapter member, the body portion is in the form of a cylindrical sleeve adapted to receive the stud element head end and to abut the interior surface of the barrel member bore, and the end portion is formed as an end Wall of the cylindrical sleeve and is stepped to present a protruding edge for impact ignition with the explosive charge. In an alternate embodiment of the firing adapter member, the body portion comprises a wire helix adapted to be threaded on the stud element head portion, and the end portion comprises an end of the wire bent to extend substantially across the end face of the stud element head portion to provide a protuberance thereat.

Brief description of the drawings FIG. 1 is a vertical sectional view taken through an explosive actuated tool according to the present invention and illustrating the stud element at its initial position;

FIG. 2 is a vertical section view similar to FIG. 1 and illustrating the stud element at its pre-firing position;

FIG. 3 is a Vertical section view similar to FIGS. l and 2, and illustrating the stud element after it has been inserted in the work surface by ring the tool;

FIG. 4 is a vertical sectional view of one embodiment of the firing adapter member of the present invention illustrated together with a stud element having a threaded head end;

FIG. 5 is a vertical sectional view of a portion of the tool of the present invention having a firing adapter member in place on the head end of a threaded stud element; and

FIG. 6 is a plan view of the firing adapter member illustrated in FIG. 4;

4 FIGS. 7, 8 and 9 are views corresponding to FIGS. 4, 5 and 6, respectively, illustrating an alternate embodiment of the tiring adapter member according to the present invention.

Description of the preferred embodiments Referring now in detail to the accompanying drawings, FIGS. 1, 2 and 3 illustrate an explosive actuated tool 10 comprising a barrel member 12 provided with a central bore 14 extending inwardly from the muzzle end of the barrel member 12. The bore 14 is formed with an enlarged outermost portion 16 that has an outwardly ared frusto-conical surface configuration for a purpose to be explained in greater detail presently, and it is formed with a chamber 18 of reduced diameter to receive an explosive charge such as a blank cartridge 20 with the ignition rim 22 thereof seated against the shoulder formed by the reduced diameter of chamber 18 and with the firing face 24 of the ignition rim facing outwardly in the bore 14. The bore 14 also includes an explosion chamber 26 formed inwardly of the cartridge chamber 18 to permit expansion of the explosive gases inwardly of the cartridge 20 when it is ignited to thereby facilitate expulsion of the spent cartridge from the cartridge chamber 18 at the completion of each firing operation of the tool 10, and the bore 14 communicates through ports 28 with an additional expansion chamber 30 formed in the barrel member 12 which reduces recoil in the tool 10` by permitting expansion of the explosive gases at the completion of the ring operation, all as explained in greater detail in the aforementioned U.S. Patent 3,172,123.

The stud element 32 which is to be driven by the tool 10 includes a pointed tip portion 34 and a head portion 36 that has an end face 38 which is stepped to present a protruding edge 40 which, when forced against the liring face 24 of the cartridge 20 with suicient impact, will cause ignition of the cartridge 20. The stud element 32 is provided with a conventional guide washer 42 that is attached to the shank of the stud element 32 with a friction fit.

To load the tool 10 for firing, the cartridge 20 is inserted in the bore 14 until it becomes seated in cartridge chamber 18 with the firing face 24 of the cartridge 20 facing outwardly. Then, the stud element 32 is inserted in the bore 14 until the annular peripheral surface of the guide washer 42 is engaged by the frusto-conical surface of the enlarged bore portion 16, the annular peripheral surface of the guide washer `42 having a diameter equivalent to a diameter of the frusto-conical bore porti0n16 intermediate the ends thereof for concentric seating thereat. When the guide washer 42 becomes seated in the frusta-conical bore portion 16, the stud element 32 will be initially restrained in the bore 14 with the tip portion 34 thereof projecting outwardly beyond the barrel member 12 and with the head portion 36 thereof spaced from the firing face 24 of the cartridge 20 as illustrated in FIG. l.

At this initial position of the stud element 32, the tool 10, even though loaded, is protected against inadvertent premature firing by virtue of the spacing between the stud element head portion 36 and the firing face 24 of the cartridge 20, and the resistance to initial inward movement of the stud element 32 in the bore 14 provided by the engagement of the guide washer 42 at the enlarged bore portion 16. Thus, if the extending tip portion 34 of the stud element 32 is accidentally contacted in a manner tending to force it into the bore 14 (i.e., if the tool is dropped so that the tip portion 34 strikes a hard surface), the guide washer 42 will be held against inward movement in the bore 14, and the force applied to the stud element 32 will be substantially entirely absorbed by the stud element 32 being forced to break the frictional hold imposed thereon by the guide washer 42, the frictional resistance to such movement being suflicient to oppose ignition impact of the cartridge 20 by the stud element 32 so that the stud element 32 will simply move to a position at which the head portion 36 of the stud element 32 lies substantially adjacent the firing face 24 of the cartridge 20 with a corresponding decrease in the outward extent of the tip portion 34 as illustrated in FIG. 2.

It is apparent, of course, that if the extending tip portion 3-4 is initially contacted by only a small inward force, the frictional hold imposed on the stud element 32 by the guide washer 42 will not be broken and the stud element 32 will remain at its initial safety position. On the other hand, while it is conceivable that the initial force applied to the tip portion 34 could be of such a magnitude as to force the stud element 32 against the cartridge 20 with ignition impact notwithstanding the frictional resistance provided by the guide washer 42, tests have been conducted in which a tool like the one illustrated in the drawings was dropped from a height of ten feet against a 1A inch steel plate and, even under these extreme conditions, the tool red only one time out of the eight times the tool was dropped. Therefore, under normal conditions, the tool of the present invention is extremely safe and for all practical purposes will not be prematurely fired by accidentally forcefully contacting the extending tip end portion 34 of the stud element 32 when the tool 10 is loaded.

It will be noted that if the stud element 32 is caused to move from its initial safety position, the frictional grip imposed thereon by the guide Washer 42 is substantially dissipated because the friction fit between the stud element shank and the guide washer 42 is thereby eliminated. Therefore, the stud element 32, with the head portion 36 thereof adjacent the firing face 24 is then in a pre-firing position and will cause ignition impact of the cartridge 20 upon further inward movement of the stud element 32.

When the tool 10 has been loaded in the aforementioned manner and the operator wishes to purposely re the tool to drive the stud element 32 into a work surface, he simply holds the barrel member 12 with the extending tip portion 34 of the stud element 32 in contact with the work surface 44 as illustrated in FIG. l. He then strikes the top end 12 of the barrel member 12 a first blow with a harnmer or similar implement which causes the barrel member 12 to move toward the work surface 44, the aforementioned frictional grip of the guide washer 42 on the stud element 32 imposing a resistance to inward movement of the stud element 32 to oppose ignition impact of the cartridge 20 whereby the stud element 32 is moved inwardly in the bore I4 from its initial position (FIG. l) to a prefiring position at which the head portion of the stud element 32 lies adjacent the firing face 24 of the cartridge 20 with a corresponding reduction in the outward extent of the tip portion 34 (FIG. 2). Preferably the reduced outward extent of the tip portion 34 is approximately four-fifths of its original outward extent. Also, it will be noted that the force transmitted to the tip portion 34 of the stud element 32 usually causes a slight indentation 44 in the work surface 44, and this serves as a guide for subsequent penetration of the work surface 44 by the stud element 32 so as to reduce the possibility of the stud element 32 ricocheting off the work surface 44 rather than being driven directly thereinto.

T he operator then strikes the top end 12 of the barrel member 12 a second blow that overcomes any remaining resistance imposed on the stud element 32 and causes subsequent inward movement of the stud element 32 so that the protruding edge 40 at the top end face 38 of the stud element head portion 36 is moved forcefully against the ring surface 24 0f the cartridge 20 to cause impact ignition thereof whereupon the expanded gases generated by the explosion of the carriage 20 will drive the stud element 32 from the bore 14 and into the work surface 44, the cartridge 20 also being expelled from its chamber 18 so that it falls down upon the stud element 32 as illustrated in FIG. 3.

Because of the powerful force thus exerted against the stud element 32 by the explosion of the cartridge 20, the tool 10 is readily employed in application which require the the stud element 32 to be driven into extremely hard work surfaces, as, for example, securing wood to steel, or steel to steel, or either wood or steel to concrete.

In some applications of the tool 10, it is desirable to drive a stud element which, because of its special function, has a head portion which is smaller than the head portion 36 of the stud element 32 previously described, a common example of such a special stud element being one having a threaded head portion which, after insertion in a work piece, can detachably receive and support a member therefrom either by directly threading the member onto the stud element head portion or by holding the member in place with a nut threaded onto the stud element head portion. However, the threaded head portion of a stud element of this sort often has a standard pitch diameter and a corresponding major diameter which is smaller than the diameter of the wall of the bore of the tool by which it is to be driven, and, in addition, the threaded head portion may not be forrned with a protruding edge portion for ignition impact of a cartridge. Therefore, a stud element having a threaded head portion of this sort is not suitable for use with an explosive actuated tool of the type previously described because the reduced diameter of the stud element head portion will permit the expanding gases of the exploded cartridge to escape through the spacing between the stud element head portion and the wall of the bore, and because there is no protruding edge for ignition impact with the cartridge. To overcome these disabilities in such stud elements, the present invention provides an adapter member which can be used with a threaded stud element to render the latter entirely suitable for use with an explosive actuated tool of the previously described type.

FIGS. 4, 5, and 6` illustrate one embodiment of a firing adapter member 46 for use with a stud element 32 having a threaded head portion 36', The firing adapter member 46 includes a body portion in the form of a cylindrical sleeve 48, and an end portion 50 that is longitudinally stepped to present a protruding edge 52 extending diametrically across the end portion 50. The ring adapter member 46 is placed over the stud element head portion 36', and the stud element 32 is then inserted in the bore 14 of the tool 10 as illustrated in FIG. 5, it being noted that in FIG. 5 the stud element 32 is located at its previously described pre-firing position rather than at its initial position spaced from the cartridge 20 so as to better illustrate the disposition of the firing adapted member 46 when the tool 10 is fired. As seen in FIG. 5, the cylindrical sleeve 48 surrounds the stud element head portion 36 to occlude the spacing between the wall of the bore 14 and the stud element head portion 36', and the protruding edge 52 lies adjacent the firing face 24 of the cartridge 20. Thus, upon subsequent inward movement of the stud element 32, the protruding edge 52 will ignite the cartridge 20 and the expending gases resulting therefrom will be contained above the head portion 36' so as to drive the stud element 32 from the bore 14.

An alternate firing adapter member 54 is illustrated in FIGS. 7, 8 and 9, and includes a body portion in the form of a wire helix 36 that is wound to a helical conguartion corresponding to the threads on the threaded stud element head portion 36', and the upper end 58 of the wire helix 56 is bent to extend diametrically across the upper end face of the stud element head portion 36 when the wire helix 56 is threaded onto the stud element head portion 36 as seen in FIG. 8 which illustrates the stud element 32 at its pre-firing position. Again, the spacing between the wall of the bore 14 and the stud element head portion 36' is occluded by the wire helix 56, and the upper end 58 of the wire provides a protuberance which will cause impact ignition of the cartridge 20 upon subsequent inward movement of the stud element 32 when the barrel member 12 is struck as previously described.

The present invention has been described above for purposes of illustration only and is not intended to be limited by this description or otherwise except as defined by the appended claims.

Weclaim:

1. An explosive actuated tool for driving an element such as a fastener stud, said tool comprising a barrel member having a bore for positioning therein a stud element to be driven by said tool and a chamber communicating with said bore inwardly of the position of said element for positioning therein a percussion ignitable explosive charge for ignition impact by inward movement of said stud element thereagainst, and means for restraining said stud element in said bore in an initial position and a stationary prefiring position, the tip end of said stud element projecting outwardly beyond said barrel member and the head end of the stud element spaced from said charge in the initial position, and when in the stationary prefiring position the stud element head lies substantially adjacent said charge and said stud element tip end has a reduced outward extent vbeyond said barrel member, said restraining means being of a magnitude to provide substantial resistance to movement of said stud element so that the stud element moves from the initial position to the prefiring position in response to a first application of force which causes inward movement of the stud element in said barrel member, said charge being ignited by stud element impact in response to an additional force being `applied to cause further inward movement of said stud element.

2. An explosive actuated tool as defined in claim 1 and further characterized in that said reduced outward extent of said stud element tip end is approximately fourefifths of its initial outward extent.

3. An explosive actuated tool as defined in claim 1 and further characterized in that said means includes a guide washer frictionally mounted on said stud element to resist movement of said stud element relative to said guide washer, and includes engaging means `associated Iwith said bore to seat said guide washer therein with said stud element at said initial position thereof and to retain said guide washer against inward movement in said bore for providing said frictional resistance to movement of said stud element from said initial position to said pre-firing position.

4. An explosive actuated tool as defined in claim 3 and further characterized in that said engaging means comprises an outwardly fiared frusto-conical surface portion formed in said bore at the outer end thereof and coaxially therewith.

5. An explosive actuated tool as defined in claim 4 and further characterized in that said guide washer has an annular peripheral surface of a diameter equivalent to a diameter of said fiared surface portion intermediate the ends thereof for concentric seating thereat.

6. An explosive actuated tool as defined in claim 1 and further characterized in that said stud element head end is smaller in diameter than the wall of said barrel member bore and spaced therefrom, and by a firing adapter member having a body portion that extends around said stud element head end and substantially occludes the spacing between said stud element head end and said barrel member bore Wall, said firing adapter member having an end portion formed with a protuberance disposed for ignition impact of said charge.

7. An explosive actuated tool as defined in claim 6 and further characterized in that said firing adapter body portion is in the form of a cylindrical sleeve surrounding said stud element head end, and in that said firing adapter end portion is formed as an end wall of said cylindrical sleeve and is stepped to present a protruding edge for ignition impact with said charge.

8. An explosive actuated tool as defined in claim 6 and further characterized in that said head end of said stud element is formed with spiral threads, in that said body portion of said firing adapter member comprises a wire helix adapted to be threaded on said stud element head portion, and in that said end portion of said firing adapter member is an end of said wire bent to extend across said stud element head end to provide a firing protuberance for ignition impact with said charge.

9. A method of driving a stud element or the like by an explosive charge comprising the steps of loading a cartridge in a chamber at the inner end of the bore of a barrel member with the firing surface of the cartridge facing outwardly for subsequent ignition impact by a stud element, positioning a stud element in the bore with the tip end of said stud element extending outwardly beyond the barrel member and the head end of the stud element spaced from the firing surface of said cartridge, applying `a force to initially move said stud element inwardly in said bore against an imposed resistance to a stationary pre-firing position at which said head end is disposed substantially adjacent said firing surface of said cartridge with a corresponding reduction in the outward extent of said tip end, said imposed resistance being sufficient to prevent ignition impact with said cartridge firing surface by said stud element head end, and then subsequently striking said barrel member with a hammer or the like to overcome any remaining imposed resistance and move said element forcefully `against said cartridge firing surface to cause ignition impact therewith by said stud element with the resulting explosion driving the stud element from the bore.

i10. A method of driving a stud element as defined in claim 9 and further characterized in that the reduced outward extent of said stud element tip end after said initial moving thereof is approximately four-fifths of its original outward extent.

11. A method of driving ya stud element as defined in claim 9 and further characterized in that said barrel member is held with the extending stud element tip end in contact with a work surface during said subsequent moving of said element, and in that said subsequent moving of said element is accomplished by moving said barrel member toward said work surface.

12. A method of driving a stud element as defined in claim 11 and further characterized in that said barrel member is held with the extending stud element tip end in contact with said work surface during said initial moving of said element, and in that said initial moving of said stud element is accomplished by moving said barrel member toward said work surface.

13. A method of driving a stud element as defined in claim 12 and further characterized in that said barrel member is moved toward said work surface by hammer blows directed at the end of the barrel member opposite the end from which said stud element tip end extends.

14. In an explosive actuated tool for driving a stud element formed with a guide washer frictionally mounted thereon, said tool comprising a `barrel member having a bore for receiving a stud element to be driven and a chamber communicating with said bore inwardly of the position of said stud element for receipt of a percussion ignitable explosive charge positioned therein for ignition by inward movement of said stud element in said bore, the improvement comprising an outwardly flared frustoconical surface portion formed in said bore to engage said stud element guide washer and restrain said stud element at an initial position with the tip end thereof extending outwardly beyond said barrel member and the head end thereof spaced from said charge, said restraint being of a magnitude to provide substantial resistance to movement of said stud element so that it moves from the initial position thereof to a prefiring position at which said stud element head end lies substantially adjacent said charge and said stud element tip end has a reduced out- 9 10 ward extent beyond said barrel member in response to a 2,708,860 5/ 1955 Arpin. rst application of force which causes inward movement 3,168,744 2/1965 Kvavle 277 10 X of the stud element in said barrel member, said charge 3 172123 3/1965 Helderman et `l 22./ 11

being ignited by stud element impact in response to an additional force being applied to cause further inward 5 movement of said stud element.

3,415,438 12/1968 IDe Caro 227-10 SAMUEL W. ENGLE, Primary Examiner References Cited UNITED STATES PATENTS U-S. C1- X.R. 2,659,273 11/1953 Trautmann. 10 89-1 2279 

